arXiv subjects

Heather Chang

Publications and source records attributed to Heather Chang.

3 recordsLinked to original sources

arXiv2026

Single-Crystal AlN Wafer-Based Bulk Acoustic Resonators for Piezoelectric Power Conversion

In this work, we demonstrate the first single-crystal aluminum nitride (AlN) wafer-based thickness-extensional (TE) mode bulk acoustic resonator for piezoelectric power conversion. The device exhibits a high series resonance 3-dB quality factor ($Q$) of 1677 and an electromechanical coupling coefficient ($k^2$) of 6.1%, highlighting the strong potential of AlN resonators for efficient power conversion. To suppress in-band spurious modes, a grounded ring structure is proposed and experimentally validated. The measured frequency-domain impedance response shows a spurious suppression of the spectrum above the resonance at 13.52 MHz. A comparative analysis with prior PZT, LN, and LT-based resonators indicates that AlN achieves a competitive figure of merit and $f \cdot Q$ product, while its material thermal conductivity is orders of magnitude higher than that of the incumbent piezoelectric power-converter resonators. The power-handling capability is expected to be superior in AlN single-crystal wafers and will be demonstrated in ongoing experiments. These results suggest that AlN offers a promising platform for compact, robust piezoelectric power converters and next-generation power electronic systems.

physics.app-ph↗

arXiv2025

Radial Mode Lithium Niobate Rosen Transformer

In this work, we demonstrate the first two-port radial-mode Rosen transformer based on 36$^{\circ}$Y-cut lithium niobate (LN) for piezoelectric power conversion. The device achieves a high transformation ratio (TF) of 16, a high electromechanical coupling factor ($k^2$) of 16.8\% and a quality factor ($Q$) of 2500, yielding an outstanding figure of merit (FoM = $Q \cdot k^2$) of 420. The fabricated transformer features a large effective turns ratio of 16 and delivers an open-circuit voltage gain of 45.56 (unloaded) and 40.57 with a load of 1 M$\Omega$ in parallel with 0.1 pF, validating its ability to provide efficient passive voltage amplification. An equivalent circuit model was developed to accurately fit both finite-element-simulated and measured admittance spectra, enabling reliable parameter extraction. These results establish LN radial-mode resonators as a promising high-performance, magnetic-less transformer platform.

physics.app-ph↗

arXiv2025

Periodically Poled Piezoelectric Lithium Niobate Resonator for Piezoelectric Power Conversion

As the demand for compact and efficient power conversion systems increases, piezoelectric power converters have gained attention for their ability to replace bulky magnetic inductors with acoustic resonators, enabling higher power density and improved efficiency. Achieving optimal converter performance requires resonators with high quality factor ($Q$), strong electromechanical coupling ($k^2$), high power handling capability, and a spurious-free response. Lithium niobate (LN) has emerged as a promising material in this context due to its high figure of merit (FoM = $Q \cdot k^2$). While previous studies on single-layer LN resonators have demonstrated high FoM values, they typically operate at relatively low resonance frequencies ($f_s$). Recently, periodically poled piezoelectric film (P3F) structures, formed by stacking piezoelectric layers with alternating crystal orientations, have shown the potential to both scale up the operating frequency and enhance the FoM compared to single-layer counterparts in piezoelectric power conversion. This work presents the first P3F thickness-extensional (TE) LN resonator for power conversion, operating at 19.23 MHz, with a large \textit{$k^2$} of 29\% and a high \textit{Q} of 3187, achieving a state-of-the-art (\textit{ $f_s \cdot Q$}) product among piezoelectric power resonators. A high-power testing procedure is performed to systematically study the nonlinear behavior and power handling of P3F LN for power applications. With further optimization, P3F TE resonators have the potential to open up a new design space for high-power and high-frequency power conversion.

physics.app-ph↗